1. Field of the Invention
This invention relates to a food mixing apparatus for use in mixing boiled rice and vinegar, for example, to prepare vinegared rice (sushi rice).
2. Description of the Related Art
A known food mixing apparatus, as disclosed in Japanese Patent Laying-Open Publication H4-71457 or H7-39326, for example, includes a base, a rotary container (or mixing container) in the form of a bottomed cylinder rotatably cantilevered by the base through a horizontal shaft, a driving device for rotating the rotary container through the horizontal shaft, and a cooling device for forcibly feeding cooling air into the rotary container through the horizontal shaft.
With this food mixing apparatus, rice, vinegar and the like are placed in the rotary container through an upper opening, then the opening is closed with a lid, and the driving device is started to rotate the rotary container about a horizontal axis. The rice in the rotary container is raised successively by the inner wall, bottom wall and lid of the rotary container, and at the same time is moved from wall surfaces counter to a direction of rotation of the rotary container. The lid has an air discharge tube projecting into the rotary container to discharge cooling air therefrom. When the lid is rotated downward, the air discharge tube divides the rice, vinegar and the like to opposite sides, thereby mixing these contents well.
In the above food mixing apparatus, however, the rotary container is rotated only in one direction about a horizontal axis. The food in the rotary container merely repeats the unvarying movement. Despite the air discharge tube projecting into the rotary container, the rice tends to become masses, making it difficult to mix the vinegar evenly therewith. A long mixing time is needed, which results in sticky rice.
In the prior apparatus, the continuous 360-degree rotation of the rotary container generates a centrifugal force that produces strong vibration. This results in an increased load acting on the connection between the rotary container and the base, thereby lowering durability of the apparatus.
This invention has been made having regard to the state of the art noted above, and its object is to provide a food mixing apparatus which moves food inside a mixing container in varied ways, thereby evenly mixing the food within a short time.
A food mixing apparatus according to this invention comprises a mixing container for receiving food, a first support frame for supporting the mixing container to be rotatable about a first axis, a first drive mechanism disposed in the first support frame for rotating the mixing container, a second support frame for supporting the first support frame to be variable in posture relative to the second support frame, and a second drive mechanism for displacing the first support frame from one posture to another.
With the above construction, food may be mixed by rotating the mixing container about the first axis while varying the posture of the first support frame supporting the mixing container. As a result, the mixing container, rather than rotating in one direction only, makes a complex movement combining the rotation with posture variations of the first support frame. The food is thereby moved in varied ways to be mixed evenly in a short time.
In this invention, the first support frame may be supported by the second support frame to be rotatable about a second axis different from the first axis. This facilitates the posture variations of the first frame, and moves the food in various directions with ease.
In particular, it is preferable to mix the food in the mixing container by oscillating the first support frame about the second axis while rotating the mixing container about the first axis. By oscillating the first support frame in this way, vibration may be reduced compared with the case of continuously rotating the first support frame 360 (. Reduced loads act on a connection between the first and second support frames and on a connection between the mixing container and the first support frame. A complex motion of the mixing container may be secured by the rotation about the first axis and reciprocation about the second axis, thereby optimizing the operation to mix the food. In this case, the first axis and the second axis preferably extend perpendicular to each other.
In a preferred embodiment of this invention, the second drive mechanism is disposed in the first support frame for varying the posture of the first support frame. Thus, both the first and second drive mechanisms are disposed in the first support frame, which facilitates a synchronous operation of the two drive mechanisms. In this case, it is easy to arrange that the first and second drive mechanisms be driven by a single drive source. This achieves a simplified construction and a reduction in cost.
In a further preferred embodiment of this invention, the first support frame includes an aerating device for feeding cooling air into the mixing container, an air intake for allowing the aerating device to draw ambient air as the cooling air, and an air outlet for discharging the cooling air from the mixing container. This construction allows the cooling air to flow smoothly into and out of the mixing container varying its posture (or oscillating) with the first support frame.
The first support frame may include an aerating device for feeding cooling air into the mixing container, the aerating device and a drive source of the first and second drive mechanisms being opposed to each other across the second axis. In this construction, an excellent weight balance may be maintained between the portion of the first support frame having the aerating device and the portion thereof having the first drive mechanism and/or second drive mechanism. This suppresses vibration due to posture variations (rotation or oscillation) about the second axis.
Further, in a preferred embodiment of this invention, the mixing container has an opening formed in a wall thereof, a ventilating tube extending through the opening, and a guide member disposed in the mixing container and extending radially outwardly of the ventilating tube to cover the opening as spaced therefrom, the opening and the ventilating tube defining a first passage therebetween for circulating air, the wall and the guide member defining a second passage therebetween in communication with the first passage, and the ventilating tube defining a third passage therein in communication with the second passage through the mixing container.
With this construction, the cooling air emerging from the first passage is guided to flow radially outwardly by the second passage communicating with the first passage. Thus, the cooling air circulates in the mixing container without being discharged immediately from the third passage. After circulating in the mixing container, the cooling air is discharged from the third passage. As a result, the food in the mixing container may be cooled evenly and efficiently in a short time.
Further, it is proposed that the wall and the guide member have a leakage preventing member disposed therebetween for allowing a circulation of air and preventing the food leaking from the mixing container. Then, the food may be prevented from leaking outside the mixing container without impairing the air circulation.
It is proposed also that the food mixing apparatus further comprises a discharge tube disposed in the mixing container for discharging air having cooled the food, and a barrier mounted in the discharge tube for stopping water flowing out of the discharge tube when the discharge tube is directed downward. With this construction, when the discharge tube is directed downward, the barrier stops a downward flow of drops of water such as dew drops formed on the inner peripheral surface of the discharge tube. Thus, the water is prevented from dripping outside to wet the frames of the apparatus and adjacent areas, or to allow dust and the like to adhere to the frames and adjacent objects. In this case, the mixing container may make a mixing movement with the discharge tube constantly directed downward (not only straight downward but also obliquely downward), or may make a mixing movement with the discharge tube temporarily directed downward.
The discharge tube extends from inside to outside of the mixing container, the barrier being formed in an inner periphery of a portion of the discharge tube projecting from the mixing container. Where the discharge tube extends from inside to outside of the mixing container as above, the portion of the discharge tube outside the mixing container, in particular, tends to be cooled by ambient air to form dew drops. The barrier formed in that portion is effective to stop an outflow of the dew drops.
Particularly, where the mixing container is constructed to mix the food by oscillating vertically between a posture to direct the discharge tube downward and a posture to direct the discharge tube upward, the dew drops and the like stopped by the barrier when the discharge tube is directed downward are returned into the mixing container when the discharge tube is directed upward. This prevents the water from accumulating in the discharge tube and overflowing the barrier. Further, with the mixing container oscillating vertically, the dew drops and the like have a minimum chance of scattering away by centrifugal force.
Other features and advantages of this invention will be apparent from the following description of the embodiment to be taken with reference to the drawings.